(1) Field of the Invention
This invention relates to the production of protein products from cottonseed. Specifically, this invention relates to a process for producing a flour product having reduced free gossypol from glanded cottonseed.
(2) Description of the Prior Art
The literature discloses that worldwide about 3.5 million tons of cottonseed proteins are potentially available from glanded cottonseed. However, cottonseed proteins are rarely utilized as a source of edible food because of the presence of pigment glands which contain toxic gossypol. This has been the major obstacle in the exploitation of this valuable source of high quality nutritious proteins. The Federal Register, Vol. 39, No. 177, page 32,735, Sept. 11, 1974, indicates that the Food and Drug Administration (HEW) specifically requires that a protein food product made from cottonseed have a content of less than 0.045% free gossypol to be considered edible.
In the literature there are a few authors and inventors who imply that they can produce edible protein products. U.S. Pat. Nos. 3,615,657, and 3,972,861 teach the production of edible cottonseed protein concentrates by what is now known as the liquid cyclone process (LCP). LCP disintegrates cottonseed kernels and separates pigment gland there from in a non-polar solvent, such as hexane.
There are several unattractive features to these processes, among which is performing the separation in a liquid medium, the filtration extraction step is relatively slow, and the separation of the product from the solvent-wet slurry is not satisfactory. Furthermore, these processes require specialized processing equipment.
U.S. Pat. No. 3,124,461 discloses moisture adjustments made on whole or split kernels with optimum moistures of about 5% to 8% prior to processing. Unfortunately, drying kernels requires more energy than drying flakes. Defatted material is milled by a non-conventional method and then subjected to gaseous classification for separation of pigment glands.
Although this patent discloses low pigment gland breakage during comminution, it can be seen in the Example 5 that considerable gland breakage has occurred since no air-classified products were produced below 0.060% free gossypol. Apparently the (1) method of extraction, (2) method of milling, and (3) method of gaseous classification, as well as other efforts of the prior art, still do not yield the desired edible protein product. This process of the prior art employs reextraction with a polar solvent to lower free gossypol content in the final product. The use of polar solvent, as those skilled in the art well know, introduces other technical problems. This disclosure indicates that a product suitable for human consumption--that is, with a free gossypol content of below 0.06%--was obtained only by reextracting the air-classified material, using 80% isopropanol, a polar solvent.
U.S. Pat. Nos. 3,895,003 and 3,965,086 deal with the preparation of protein concentrates from oilseed flours by employing air classification. These two disclosures are not concerned with the removal of pigment glands and the subsequent production of low gossypol cottonseed flours. In both instances only glandless or deglanded flours were employed.